1. Field of the Invention
The present invention relates to a liquid discharge head for discharging a desired liquid by generating a bubble created by acting thermal energy to the liquid, a method for manufacturing such a liquid discharge head, and a liquid discharge apparatus.
2. Related Background Art
An ink jet recording method, i.e., a so-called bubble jet recording method in which a condition change including abrupt volume change (generation of bubbles) is generated and ink is discharge from a discharge port by an action force based on the condition change and the discharged ink is attached to a recording medium to form an image on the recording medium is well known. As disclosed in U.S. Pat. No. 4,723,129, in a recording apparatus utilizing such a bubble jet recording method generally includes discharge ports for discharging the ink, ink flow paths communicated with the discharge ports, electrical/thermal converters (as energy generating means) disposed in the ink flow paths and adapted to generate energy for discharging the ink.
According to such a recording method, since a high quality image can be recorded at a high speed with low noise and the discharge ports can be arranged with high density in a recording head carrying out the recording method, there are provided many excellent advantages that an image having high resolving power and even a color image can easily be recorded by a compact apparatus. Thus, recently, the bubble jet recording method has been applied to various office equipments such as printers, copying machines and facsimiles and has also been utilized in industrial systems such as a printing apparatus.
By the way, the electrical/thermal converter for generating energy for discharging the ink can be manufactured by using a semiconductor manufacturing process. Thus, a conventional head utilizing a bubble jet technique is constituted by forming the electrical/thermal converters on an element substrate composed of a silicon substrate and by forming grooves defining the ink flow paths above the converters and by bonding a top plate made of a resin such as polysulfone, glass or the like thereto.
Further, there has been proposed a technique in which, by utilizing the fact that the element substrate is composed of the silicon substrate, not only the electrical/thermal converters are formed on the element substrate but also drivers for driving the electrical/thermal converters and temperature sensors used for controlling the electrical/thermal converters in accordance with a temperature of a head and their associated drive control portion are provided on the element substrate (for example, refer to Japanese Patent Application Laid-Open No. 7-52387). The head in which the drivers and the temperature sensors and the associated drive control portion are provided on the element substrate has already been put on practical use, thereby contributing to improvement of reliability of the recording head and compactness of the apparatus.
In the conventional liquid discharge head in which the temperature sensors are provided on the element substrate, the temperature sensor was mainly used for measuring the temperature of the element substrate. However, recently, as high density recording has been progressed, an amount of ink discharged by one discharging has been made smaller more and more, with the result that, rather than the temperature of the substrate, condition and kind of the ink such as temperature and density of the ink itself have affected an influence upon the recording. That is to say, as the ink discharging amount is decreased, the difference in discharge amount due to the condition of ink which did not arise serious problem conventionally has been highlighted as dispersion in discharge amount.
In such a circumstance, in the arrangement of the temperature sensors in the conventional liquid discharge head, it was difficult to detect more correct ink condition. The reason is that, although the temperature sensors in the conventional liquid discharge head are flatly formed on the surface of the element substrate together with the electrical/thermal converters and the drive control portion by using the semiconductor wafer process, in the vicinity of the surface of the element substrate, flow of ink is apt to be stagnated and great temperature gradation is created by the influence of heat from the electrical/thermal converters.
An object of the present invention is to provide a liquid discharge head, a substrate for use in such a liquid discharge head and a method for manufacturing such head and substrate, in which stable discharging is permitted by detecting a condition of liquid to be discharged with high accuracy.
To achieve the above object, according to the present invention, there is provided a liquid discharge head comprising a plurality of discharge ports for discharging liquid, first and second substrates for defining a plurality of liquid flow paths communicated with the discharge ports, and a plurality of energy converting elements each disposed in each of the liquid flow paths and adapted to convert electrical energy into discharge energy for liquids in the liquid flow paths, wherein sensors for detecting behavior of the liquid are provided in the respective liquid flow paths as solid structure portions protruded from walls of the liquid flow paths.
According to another aspect of the present invention, there is provided a liquid discharge head comprising a first liquid flow path communicated with a discharge port, a second liquid flow path having therein a heat generating body for generating a bubble in liquid by applying heat to the liquid, and a movable member disposed between the first and second liquid flow paths and having a free end at a downstream side thereof along a liquid flowing direction and adapted to transmit a pressure caused by generating of the bubble in the second liquid flow path to the first liquid flow path by displacing the free end toward the first liquid flow path on the basis of such pressure, wherein a sensor for detecting a condition of the liquid located on a wall of the first liquid flow path at least between the discharge port and the free end of the movable member is provided, and wherein first liquid supplied to the first liquid flow path and second liquid supplied to the second liquid flow path are both discharged from the discharge port by the generation of the bubble in the second liquid.
According to a further aspect of the present invention, there is provided a liquid discharge apparatus comprising the above-mentioned liquid discharge head, wherein recording is effected by discharging liquid onto a recording medium by driving the energy generating element while adjusting the energy generating element on the basis of output voltage obtained in a circuit portion.
According to a still further aspect of the present invention, there is provided a method for manufacturing a liquid discharge head substrate used in a liquid discharge head for discharging liquid by applying discharge energy to the liquid and having a semiconductor substrate on which an energy converting element for converting electrical energy into the discharge energy is formed, comprising the steps of forming a substrate layer including a semiconductor material on the semiconductor substrate in a predetermined pattern, forming a detecting portion having electrical property changed in accordance with behavior of the liquid to be detected and a wiring for electrically connecting the detecting portion to an electric circuit formed on the semiconductor substrate on the substrate layer, and forming a protection layer including a semiconductor material for protecting the wiring on the substrate layer on which the detecting portion and the wiring were formed.
According to a further aspect of the present invention, there is provided a method for manufacturing a liquid discharge head including a plurality of discharge ports for discharging liquid, first and second substrates for defining a plurality of liquid flow paths communicated with the discharge ports, and a plurality of energy converting elements disposed in the liquid flow paths and adapted to convert electrical energy into discharge energy for liquids in the liquid flow paths, comprising the steps of forming a detecting portion having electrical property changed in accordance with behavior of the liquid to be detected and a wiring electrically connected to the detecting portion on at least one of the first and second substrates, and forming a protection layer including a semiconductor material for protecting the wiring on the substrate layer on which the detecting portion and the wiring were formed.
Incidentally, in the specification, terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are used in connection with a liquid flowing direction from a liquid supply source toward a discharge port through a bubble generating area (or a movable member), or a constructural direction of this constitution.